Accretion definition, an increase by natural growth or by gradual external addition; growth in size or extent. See more.
Alveoli are tiny sacs within our lungs that allow oxygen and carbon dioxide to move between the lungs and bloodstream. Learn more about how they function and quiz your knowledge at the end.
Alveoli. The epithelium of the alveoli, contains two main types of cells: 1. type I pneumocytes: large flattened cells - (95% of the total alveolar area) which present a very thin diffusion barrier for gases.They are connected to each other by tight junctions.2. type II pneumocytes (making up 5% of the total alveolar area, but 60% of total number of cells).lveoli. The epithelium of the alveoli, contains two main types of cells: 1. type I pneumocytes: large flattened cells - (95% of the total alveolar area) which present a very thin diffusion barrier for gases.